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  1. #1
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    NEBB Stepwise vs. Proportional Balancing Methods - Preference?

    Wondering what the preference is for stepwise vs. proportional balancing methods based on everyone's experiences for air/hydronic given time and effort required for each. Or if there is another more efficient general approach? Per NEBB 2005 definitions for hydronic:

    Stepwise Balancing Method:

    a. Verify that all balancing, control, and isolation valves are wide open.
    b. Determine total system volume by the most appropriate method.
    c. Calculate the percentage of actual hydronic flow to design hydronic flow.
    d. Adjust the pump volume to approximately 110% design flow if possible.
    e. Measure the flow at all balancing valves.
    f. Starting at the pump, as the terminal units closest to the pump will typically be the highest, adjust the balancing valves to a value approximately 10% below design flow requirements.
    g. As the adjustment proceeds to the end of the system the remaining terminal unit flow values will increase.
    h. Repeat the adjustment passes through the system until all terminal units are within +-10% of design flow requirements and at least once balancing valve is wide open.
    i. If necessary, adjust the pump volume to set all terminal units at design flow +-10%.
    j. Re-measure all terminal units and record final values.
    k. Mark or set all memory stops on all balancing valves so that the adjustment may be restored if necessary.

    Proportional Balancing Method (Ratio Method)

    a. Verify that all balancing, control, and isolation valves are wide open.
    b. Determine total system volume by the most appropriate method.
    c. Calculate the percentage of actual hydronic flow to design hydronic flow.
    d. Adjust the pump volume to approximately 110% design flow if possible.
    e. Measure the flow at all balancing valves.
    f. Compute the ratio of measured flow to design flow for each terminal unit.
    g. The balancing valve serving the terminal unit at the lowest percentage of design flow is not adjusted in this procedure.
    h. Adjust the balancing valve serving the terminal unit with the next (second) lowest percentage of design until both terminal units are the same percentage of design. These terminal units are now in balance.
    i. Adjust the balancing valve serving the terminal unit with the next (third) lowest percentage of design until all three terminal units are at the same percentage of design, and in balance.
    j. Continue this procedure until all remaining terminals have been adjusted to be in balance at approximately the same percentage of design flow.
    k. If necessary, adjust the pump volume to set all terminal units at design flow +-10%.
    l. Re-measure all terminal units and record final values.
    m. Mark or set all memory stops on all balancing valves so that the adjustment may be restored if necessary.

  2. #2
    Join Date
    Aug 2019
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    Both methods will work and get you acceptable results . I use the first method with some changes . When I start pulling down the coils closest to the pump I don't pull them down 10% lower than design . I pull the highest ones down 15- 20% low . When when you pull it down 15- 20% or so this first coil ( or second or third ...etc ) will only have to increase 10% to be within 10% of design . The first third of the coils I will pull down 15-20% , the middle third 5-10% low of design and then the last third right at design or maybe 5% low of design . I balance air the same way and can mostly get it right in 2 ( or 1.5 ) passes . The other thing that is very important is look at the lowest flow coils ( or grilles ) first . If the strainer is a bit dirty or a damper is a little bit pulled down you will sometimes sacrifice the whole system to push fluid to that low device . Always check the lowest devices first , its easier to open one damper than to pull 10 down trying to force the air ( or water ) there. Hope this helps .

  3. #3
    Join Date
    Feb 2016
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    That method is for constant volume systems. I always set the flow for 120% (if possible) prior to balancing. It takes some experience but after a while you get a good idea of where to set each circuit setter on the first pass. It depends on the configuration of the system.
    On hot water systems that are under designed that system will not work. You will run into one sooner or later.
    No man can be both ignorant and free.
    Thomas Jefferson

  4. #4
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    You should always add up all of the required coil gpm's and compare it to the design of the pump . This will ensure you don't try to balance an under designed system . Many hospitals have this problem . In this case the best you can do is drive each reheat to full heat and test the leaving air temperature to make sure they are working .

  5. #5
    Join Date
    Feb 2016
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    Louisburg Kansas
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    Fortunately hot water heat is very forgiving. A lot easier than chilled water.
    No man can be both ignorant and free.
    Thomas Jefferson

  6. #6
    Join Date
    Aug 2019
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    Central Florida
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    ^^^ yup .

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